1. Institute of High Energy Physics Chinese Academy of Sciences
Welcome EPICS'02
2002 EPICS Seminar
Institute of High Energy Physics
Chinese Academy of Sciences
20-22 August, 2002

2. Introduction to BEPCII EPICS Seminar 2002 （August 20, 2002, IHEP）
From BEPC to BEPCII
Basic Design
Key Technologies
Budget and schedule
Summary

3. (1) From BEPC to BEPCII
Status of the BEPC
Why BEPCII
What is BEPCII

4. 1.1 The Status of the BEPC

5. The Layout of BEPC storage ring

6. Main Parameters Beam Energy (E) 1.0 ~ 2.5 GeV
Revolution frequency (fr) MHz
Lattice Type FODO + Low-b Insertions
*x -function at IP (*x/ *y) 1.3/0.05 m
Transverse Tune (x/y) /6.8 (Col. Mode) /4.75 (SR Mode)
Natural Energy Spread (e) E 10-4
Momentum Com. Factor (p) (Col. Mode) (SR Mode)
Hor. Natural Emittance (x0) GeV, mmmr
RF Frequency (frf) MHz
Harmonic Number (h)
RF Voltage (Vrf) ~1.6 MV
Bunch Number (Nb) 1*1 (Col.), 60~80 (SR)
Maximum Beam Current GeV (Col.,) 130mA (SR)
Luminosity 1030 cm-2 GeV, 11031 cm-2

7. Statistics of 00-01 Operation
Fault
Start-up
Injection 6% 4%
12%
BSRF MD
26%
10%
BES
42%

8. Daily J/y operation of BEPC
Period Days Beam time (hrs.) J/y events Lmax(1030cm-2 s-1) t(hrs) M M

9. Physics results from BEPC/BES

10. BSRF dedicated operation
70 days with three times for about 300 users every year
Imax=140 mA, ex0=76 nm, t=20~30 hrs., Ninj=2

11. Synchrotron radiation application with BSRF

12. 2.1 Why BEPCII
BEPC/BESI collected 9 106 J/y events in about two years;
Upgraded BEPC/BESII obtained 5107 J/y events in two years;
BEPC/BESI collected 4 106 y events;
BEPC /BESII operated for y from Nov. 23, 2001 to March 13, 2002;
With 1 106 a week, 1.4107 y was collected in 100 days;
Nice physics results are expected;
For our physics goal, 6 109 J/y 2109 y per year are expected  BEPCII/BESIII!

13. 1.3 Luminosity Strategy of the BEPCII
Multy-bunch kbmax~400, kb=1  93
Choose large ex & optimum
param.: Ib=9.75mA, xy=0.04
Micro-b:by* =5cm  1.5 cm
SC insertion quads
Reduce impedance +SC RF
sz =5cm  <1.5cm
(LBEPCII/ LBEPC) D.R.=(5.5/1.5) 93  9.8/35=96
LBEPC=1.010 31 cm-2s-1  LBEPCII =110 33 cm-2s-1

14. (2) The Basic Design The double ring structure of BEPCII
Design Goals and Main Parameters
Lattice and Dynamic Aperture
Beam Collective Effects
Beam Lifetime & Average Luminosity

15. 2.1 The double ring structure of BEPCII

16. Mock-up of the double ring installation
There is no showstopper for the transportation, installation, mounting and dismount of the magnets.
The existing monuments for survey and alignment will be covered by the inner ring magnets. New monuments will be fixed on the wall of the tunnel.
The antechamber of the positron ring needs to be carefully designed to fit the crucial space between two rings;
The cable system, the cooling-water system, the pressure-air system and others need to be rearranged.

17. Magnet girder and pre-alignment

18. 2.2 Design Goals and Main Parameters

19. Main Parameters

20. 2.3 Lattice and Dynamic Aperture

21. 2.4 Single beam collective effects
Bunch length and impedance
Vrf = 1.5MV, Z/n|eff0.2, Ith = 37mA  Ib = 9.8mA, l ~ 1.3 cm
Beam-cavity interaction (with KEKB SC cavities)
Resistive wall
x/y = 6.6/7.6, Nb = 99, Ib = 9.8mA,  = 4.3ms;
Ion effects
Electron cloud instability:
Antechamber with TiN coating for e+ ring
Bunch feedback：tL=5 ms, tT =2 ms 
Single beam instabilities can be damped !

22. 2.5 Beam-beam effects
Head-on beam-beam effect: similar to BEPC  x=0.04 has been demonstrated
Parasitic beam-beam effect 
c=112 mrad
Horizontal crossing angle c 
(5.5-11)2 mrad (BEPCII), 2.32 mrad (CESR)
112 mrad (KEKB), 12.5 2 mrad (DAFNE)
Beam-beam simulation for BEPCII with BBC code has shown that the beam-beam parameters and crossing angle of 11 mrad are acceptable.

23. 2.5 Beam Lifetime and Average Luminosity
Taking t =1.35 hrs., tf= 0.4 hr. and L0=11033 cm -2s-1, the optimized collision time is calculated as 1.0 hrs. and the maximum average luminosity is calculated as Lmax~ 0.51033 cm-2s-1. The top-off injection will further improve the average luminosity.

24. (3) Key Technologies Injector Upgrades 500 MHz SC RF System
SC Micro-b Quads and IR
Magnet System
Power Supply System
Injection Kickers
Vacuum System
Instrumentation and Feedback
Control Upgrade

25. BEPCII will apply state of art technologies

26. 3.1 Injector upgrading Basic requirement:
Higher intensity: positron injection rate  50 mA/min.;
Full energy injection with E=1.55 ~ 1.89 GeV;
To enhance the current and energy of the electron beam bombarding the target and to reduce the beam spot;
To design and produce a new positron source and to improve its focusing;
To increase the repetition rate from present 12.5 Hz to 50 Hz.
To consider multi-bunch injection (fRF/fLinac=7/40);

27. The measures to increase positron intensity

28. BEPCII Positron Source

29. 3.2 500 MHz SC RF System Basic requirement
Sufficient RF voltage for short bunches.
Sufficient high RF power.
Suppressing the instabilities related to RF system.
Stable and reliable RF system

30. RF Cavity in BEPCII Tunnel

31. 3.3 SC Micro-b Quads and IR

32. 3.4 Magnets System
New arc magnets

33. Two-in-one Quadrupole IQ1

34. Septum Bending magnet ISPB
Magnetic length 0.6m
Magnetic Field T
Theckness mm
Aperture 78mm2
Current A
Current density A/mm2

35. (5) Power Supplies System

36. 3.6 Vacuum System Vacuum pressure
The BEPCII poses two challenges to the vacuum system, one is vacuum pressure （Arcs: 810-9Torr， IR: 510-10Torr）, other is the impedance.
Vacuum pressure
Electron Ring Positron Ring

37. Vacuum Chamber Design

38. 3.6 Injection Kickers

39. 3.7 Instrumentation and Feedback
Beam Position Monitor
Bunch Current Monitor
Beam Feedback System
Synchrotron Light Monitor
IP beam position control ……

40. 3.8 Control System BEPC BEPCII  WS console Ethernet PC subsystems
VAX 4500
Injection
Beam diagnostic
Linac
CAMAC
PS, Vacuum, RF
BEPCII 

41. (4) Budget and Schedule
The budget of BEPCII project is estimated as 640 MRMB. It is scheduled to finish in 4 years.

42. (5) Summary
BEPC has been well operated with many exciting HEP and SR results for 13 years since it was put into operation in 1989.
BEPCII is proposed as micro-b plus multibunches with two rings and its design luminosity is order of magnitude higher than present BEPC in energy range of J/y, y  and y.
Some key technologies need to be developed to achieve the goal of BEPC II.
The international collaboration will be promoted in order to accomplish this challenging and exciting project on schedule and budget.

43. May the EPICS’02 be a Great Success !